1. Field of the Invention
The present invention relates, in general, to a different shrinkage mixed yarn produced by mixing the same or different grey yarns having different thermal shrinkage and, more particularly, to a method of producing such mixed yarns.
2. Description of the Prior Art
In the prior art, different shrinkage mixed yarns are produced through the following two methods. That is, such mixed yarns may be produced by separately spinning two different grey yarns prior to mixing the separately spun grey yarns into a single yarn at a drawing step. Alternatively, such mixed yarns may be produced by mixing two different grey yarns into a single yarn after the two different grey yarns are separately spun and drawn. However, the two methods for producing mixed yarns are problematic in that they individually have a long and multi-step process, thus increasing the production cost of the resulting yarns and causing the appearance of the resulting yarns to be spoiled. Another problem experienced in the above methods is that the separately processed core and effect yarns have to be doubled into a single yarn, thus causing a difference in dyeing exhaustion between the core and effect yarns and reducing the quality of fabrics produced by the resulting mixed yarns. Such a problem caused by the difference in the dyeing exhaustion becomes worse when different polymers are used as high and low shrinkage parts of a resulting mixed yarn.
In the typical methods for producing mixed yarns, resulting yarns have to be produced with reduced productivity since the operational speeds of spinning and drawing machines used in the methods are limited. Such reduced productivity also increases the production cost of the resulting yarns.
Japanese Patent Laid-open Publication No. Hei. 7-243,144 discloses a method of causing a desired difference in thermal shrinkage between core and effect yarns by making the thermosetting properties of the two yarns different. In the above Japanese method, the difference in thermosetting properties between the core and effect yarns is achieved by attaching a hot tube to a spin draw spinning machine. However, this method is problematic in that it has to be provided with a very expensive and awkward hot tube.